The decomposition of recidivism rates shows that this reduction is driven by marginal recidivists who, but for Medicaid expansions, would be reconvicted for the type of crime for which they were previously convicted. Analyses of potential mechanisms show an increase in criminal justice referrals to addiction treatment, which may reduce impulsive behavior. Back-of-the-envelope calculations also indicate that there are substantial cost reductions from providing Medicaid coverage to former inmates.